The Sigma APO Macro 180mm F2.8 EX DG OS HSM ($1,699 direct) is an impressive macro lens with a rather long focal length, fast aperture, and 1:1 magnification. It’s available for Canon, Nikon, Sigma, and Sony/Minolta cameras, and can be used on both full-frame and APS-C bodies. It’s a bit more expensive than Sigma’s older 150mm F2.8 EX DG OS HSM APO Macro, a lens that impressed us when we tested it, but we feel that the extra sharpness it delivers makes it worthy of our Editors’ Choice award.

It’s a big lens. It measures 8 by 3.7 inches (HD) and if you’d like to use a filter you’ll have to reach for one with an 86mm thread to fit into its huge front element. It’s also heavy—just about 3.6 pounds. The reason for its size is its close focus capability; you can find standard lenses in this focal range that are smaller and lighter, but they won’t focus on objects as close as 18.5 inches from your camera’s image sensor. That allows for 1:1 magnification—when the lens is focused on objects that close, the image projected onto your camera’s image sensor matches the real life object exactly in size. That’s typical for a lens of this class; the Canon EF 180mm Macro f/3.5L USM is capable of 1:1 magnification as well. It’s smaller at 7.3 by 3.3 inches and lighter at 2.4 pounds, but it doesn’t feature optical stabilization.

Most macro lenses that are 100mm or longer deliver 1:1 magnification, but having one this long allows you to work further away from your subjects. There are pluses and minuses to this. On the plus side, working a little further away helps if you don’t want to cast a shadow on a flower or insect in the wild. On the minus side, you’ll likely want to stop down your lens when working very close, depending on how much depth of field you want to get, and doing so with a longer lens requires a shorter shutter speed to get a crisp shot. If you think you’ll prefer a shorter macro lens, consider the Carl Zeiss Makro-Planar T* 2/100 or Makro-Planar T* 2/50. Both are excellent lenses and can open up to f/2, but keep in mind they are manual focus only and only deliver 1:2 magnification. There are plenty of autofocus 1:2 macro lenses available in the 50 to 60mm focal range, but none that we’ve yet had a chance to review.

Sigma supplies a tripod collar, two lens hoods (one for full-frame, one for APS-C), and a carrying case with the lens, along with the standard front and rear caps. If you’re planning on using the lens on a tripod or a monopod, it’s a good idea to use the collar. It helps to better center the weight, which will lead to steadier shots. There are a couple of control switches on the lens itself. You can control the optical stabilization system via the OS switch. It has three settings—Off, 1, and 2. Turning it off is recommended when using a tripod, mode 1 is for standard shooting situations, and mode 2 is for those times when you plan on panning your camera to the left or right during a shot. There’s also a switch to change between automatic and manual focus, and a focus limiter control. That lets you limit the distance over which the autofocus system will hunt; you can set it for the full range of the lens, from 0.67 meters to infinity, or from 0.47 meters to 0.67 meters.

I used Imatest to check the sharpness of the lens when mounted on the 36-megapixel Nikon D800. It’s impeccably sharp. At f/2.8 it manages 2,956 lines per picture height, well in excess of the 1,800 lines we require of a sharp photo, and it performs well from edge to edge. Stopping down to f/4 delivers a slight improvement to 2,978 lines, and you’ll get the best resolution at f/5.6—3,552 lines. Distortion is a negligible 0.2 percent, which is irrelevant in field conditions. Sigma’s older 150mm Macro only managed 1,843 lines on the D800 at f/2.8, and did its best at f/8, notching just shy of 3,000 lines.

If you’re in the market for a macro lens and want one with a longer focal length, you should give strong consideration to the Sigma APO Macro 180mm F2.8 EX DG OS HSM. It’s extremely sharp, is optically stabilized, and the focus limiter function allows it to focus quickly enough to double as a standard telephoto optic. We like it better than the Canon EF 180mm Macro f/3.5L USM, which is priced in the same ballpark but lacks image stabilization. If you’re on a budget you might want to look at the Sigma 150mm F2.8 EX DG OS HSM APO Macro; it’s not as sharp at its maximum aperture, but improves when stopped down. It also offers stabilization, and sells for about $600 less. But our Editors’ Choice award is for exemplary products and, even though the 180mm is a bit on the pricey side, we feel the extra sharpness it delivers is worth the cost.